Apparatus for bright-annealing of metals



Aug. 11, 1959 K. H. FR lTZ 2,899,192

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I APPARATUS FOR BRIGHT-ANNEALING OF METALS Filed May 24, 1957 5 Sheets-Sheet 5 I INVENTOR. K454 H'f/VEICH F5172 2,899,192 Patented Aug. 11, 1959 APPARATUS FOR BRIGHT-ANNEALING OF METALS Karl Heinrich Fritz, Hagen, Westphalia, Germany Application May 24, 1957, Serial No. 661,528

7 Claims. (Cl. 266--) The present invention relates to a process and device for bright-annealing of metals, moreparticularly of fine wires down to very small diameters.

The device consists of an annealing oven, a container which, after having been charged with the goods to be annealed, is placed into the oven having a wide opening at the bottom, through which the container is lifted into position by suitable hoisting means.

The annealing process is carried out in a high vacuum which is a conventional method in this art. The annealing containers are evacuated to a high degree before annealing is started. As against the vacuum ordinarily formed by heating, this has the advantage that the degree of evacuation can be chosen independently of the annealing temperature. Due to the high vacuum, oxygen is removed from the container, so that a combustion of residual lubricating oils is decreased. On the other hand, any adhering particles of grease or oil will become loosened during the heating process from the goods to be annealed and will be readily evaporated.

According to the present invention, the annealing vessel is to be evacuated several times during annealing, whereby residual particles of grease or oil from the drawing process will be completely removed. After having carried out the process according to the invention it was found that the metal was perfectly free of any contaminating lubricant and the goods were bright and nontacky.

It is a known fact that annealing vessels such as containers or retorts, which have been under high vacuum, require a long time to cool down, particularly in the lower temperature zones. While it has already been proposed to shorten the cooling period by admitting cold inert protective gas, for instance nitrogen, to the annealing container after the annealing treatment it has been discovered according to the invention that it is preferable to circulate the gas, because this promotes cooling. It is particularly advantageous to cool the gas during the circulation, whereby a gradual instead. of abrupt cooling is accomplished. In this manner heat is removed at a higher rate from the container by means of the protective gas so that the heat transfer figures are increased both at the surface of the annealed goods and at the inner wall of the container. The gas serves as carrier which transfers the heat from the annealed goods to said inner container wall.

It is a further improvement according to the invention to provide means for accelerated heat dissipation at the outside surface of the annealing container. For this purpose a current of coolant, e.g. cold air, is passed along the outer wall. One Way of carrying this measure into effect is to place a cooling hood on the container to be cooled, which has at the bottom end openings for air admission, and in the upper part, e.g. at the top, an air circulating unit, which aspirates the admitted air along the wall of the annealing container and ,expels it at the top into the open air.

The invention also provides an apparatus for carrying out the process according to the invention. The apparatus comprises an annealing oven, an annealing container for receiving the goods, e.g. fine wires, to be annealed, lifting means for placing the annealing container charged with the goods, into the oven, a vacuum pump for evacuating the annealing container during the process and various pipe lines for connecting the several parts.

One embodiment of the invention provides sealing means by which the container will be sealed hermetically after having been placed in the oven and the space within the oven will be maintained at the same pressure as the container.

It is one preferred feature to provide means for alternatively connecting the annealing container to a high vacuum pump and to a charging unit for protective gas.

As mentioned before it is a feature of the invention to provide a cooling means for the annealing container, e.g. a hood to be slipped over the container so as to leave free an annular space for air circulation under the action of a fan or the like.

A further detail consists in the arrangement of closed annular cooling ducts near the sealing means for the oven and for the annealing container, part of the ducts being in wall-towall arrangement with the apparatus to be cooled and the walls of the apparatus units to be cooled forming themselves a part of the cooling ducts.

The invention further provides a vacuum cock of special construction for insertion into the suction line leading from the vacuum pump to the annealing container or annealing oven, respectively. This cock contains a pressure relief valve in the part between the valve seat and the annealing container, said valve being preferably connected to the casing of the cock.

According to one embodiment of the cock construction, the relief valve is arranged at or in the bottom of the cock casing toward the side of the annealing con tainer; in this construction a cap having outlet openings to the atmosphere is attached to the bottom of the easing, the bottom serving also as a valve seat for a spring supported plate valve, the spring acting normally to close the valve.

Further details will become apparent from the detailed description hereinbelow.

In the accompanying drawings an annealing apparatus is shown by way of example, but it should be understood that this is given by wayof illustration and not of limitation and that many changes in the details can be made without departing from the spirit of the invention.

In the drawings,

Fig. 1 is a general diagrammatic view of the entire apparatus;

Fig. 2 is a partial section through the cooling chambers;

Fig. 3 illustrates a vacuum cock with pressure relief valve;

Fig. 4 is a diagrammatic showing of the cooling system, and

Fig. 5 is a view of the annealing container proper with cooling hood.

The bright-annealing apparatus shown in Fig. 1 comprises an annealing oven P, which may be supported on columns in a stationary manner, or which may be of the movable (hood)-type; furthermore, a movable container B with base 7, a hydraulically or pneumatically operated lifting device G for hoisting the container B and its base 7 into the oven; a vacuum pump H with a cock and pressure relief valve J, and a connecting hose K between pump H and valve J.

Before annealing is eifected, the annealing container B is first highly evacuated and then lifted into the oven F by means of hoisting device G. There it remains to the termination of the annealing treatment. In order that A, 3 the oven chamber can be evacuated so as to have about the same pressure as container B, gaskets M may be provided, more fully shown in Fig. 2; and a branch vacuum line K is arrangedior connecting chamber 14 to pump H, said line containing a relief valve 1.

A more detailed showing of the sealing and cooling arrangements are given in Fig. 2. There, a rubber gasket 16 is shown for providing a complete seal between the annealing hood of container B and the base 7. This seal needs cooling. For that purpose, a duct 18 for the coolant is arranged below a channel-shaped member 17 which receives the gasket 16. Duct 18 is preferably so designed that it surrounds the base 7 and water is constantly circulated therethrough. Also, for preventing heat transmission from hood 15 to gasket 16, another annular duct 19 for coolant is provided near the bottom end of the hood 15.

As mentioned above a cock with a pressure relief valve is arranged in the suction line between vacuum pump H and container B. This cock and valve which is shown in greater detail in Fig. 3, is provided for rendering the apparatus accident-proof. This is accomplished by preventing the building-up of dangerous super-pressure in container B, which may, e.g., occur when through a faulty manipulation of the operator water enters from the water pump into the highly heated annealing container.

The casing of the cock is designated by 20; into the casing, two connecting pieces, 21 and 22, open from opposite directions. The tubular piece 21 connects the vacuum pump with a space 23 above the valve seat 24. Through space 23 a valve stem carrying a valve plate (not shown) passes up to a hand wheel 25 by which it is rotatable. The other tubular piece, 22, which opens into a space 27, below valve seat 24, makes connection with container B to be evacuated.

The bottom portion 28 of valve casing 20 converges into a cylindrical portion surrounding a recess 29 in com munication with space 27. The wall surrounding the recess has an external thread to which is screwed a cap 31 having outlet openings 30.

The bottom of the valve casing, which is open, forms a valve seat for a plate valve 32 having a projection 33 which serves as a guide means for a spring 35 bearing against the bottom of cap 31, where it is mounted on a stub 36. Spring 35 bears with its upper end on an annular sleeve 34 surrounding plate 32 and supporting a sealing ring 37. Elements 3037 form the pressure relief valve, which is normally closed by the force of spring 35, but which opens when an excess pressure is created in the evacuated container, and permits the escape of pressure fluid through openings 30 in cap 31. After equalization of pressure has been reached, the relief valve will automatically be closed.

The cooling system which is shown in Fig. 4 comprises a receptacle A for protective gas, a cylinder E containing such gas, a cooler D for the gas, and a pump C for circulating the latter. A number of connecting pipes and valves are likewise provided, which will be described hereinbelow as the operation of the system is explained. B again designates the annealing vessel. The protective gas, e.g. oxygen-free nitrogen is passed from the cylinder E or receptacle A by way of line 13 to the evacuated container B after the annealing period. On its way, the gas passes an oxygen-absorbing filter, containing e.g. copper wool. After having rinsed the contents of container B, the gas may either be made to escape into the open, or it may be returned to the process through line 12, over cooler D, pump C and line 12a, back to A. Valves 1 and 2 are provided in lines 12 and 13, respectively, so that container B can be separated from the system after evacuation or after cooling. With valve 1a open and valve 1 closed, gas will be capable of escaping into the open.

For operating the plant, cylinder B may be connected to receptacle A over valve 3, which may be operable by hand or by remote control, e.g. by means of a switch pneumatically actuated by the pressure in the receptacle. A pressure relief valve 4 is provided for preventing excess pressure from building up in receptacle A. Also, a manometer 5 serves for the reading of the pressure prevailing in the system.

Instead of the receptacle A and the gas cylinder E, a unit for generating the protective gas may be connected to the system. Moreover, as a means for maintaining contant pressure, some other receptacle may be used instead of the one shown at A, e.g. a bell tank with a water seal at the bottom.

The protective gas passed or pumped through container B assures dissipation of heat by convection, on the one hand, and promotes heat transfer of the annealing hood to the surrounding atmosphere. After a temperature of 40 C. has been reached by cooling, the valve 3 is closed and the maximum quantity of gas possible is withdrawn from container B by means of pump C. Then valve 1 is closed, a valve 1a is opened for admission of air to container B, which can then be opened.

In Fig. 5 an additional device is illustrated which serves for an acceleration of the cooling of container B. When the container is surrounded by air, heat dissipation from the wall of the container occurs by natural circulation. Due to the filling of the container B with protective gas, after the annealing in vacuo has been terminated, and due to the circulation of that gas, heat will pass readily from the annealed goods to the wall of the container. In order to accelerate further the heat transfer from the wall, a special cooling hood 11 is provided to be slipped over the container B, leaving free annular space 8 between the wall 6 of container B and the hood. Air admission openings 9. are provided in the bottom portion of hood 11 and an air circulating unit 10 is arranged on top thereof, which aspirates the air admitted at the bottom and expcls it laterally. Loss of heat from the wall of the annealing container is considerably speeded up in this manner.

The above described embodiment of the apparatus according to the invention can be modified in various ways without departing from the spirit of the invention.

For instance, high vacuum annealing could be carried out in an oven, into which the annealing container could be placed from the front or from the sides, instead of being lifted into it from below.

What I claim is:

1. An apparatus for bright-annealing of metal articles, including wires of small diameter, which comprises an oven having a wide opening at the bottom, an annealing container, hoisting means for lifting said container through said opening into said oven, a high vacuum pump with connecting lines to said container and said oven, respectively, for evacuation thereof, cock means in said lines for connecting said vacuum pump to said container and oven during the annealing operation, and a cooling system in said annealing apparatus including a unit containing protective gas, said unit comprising lines for connecting it to said annealing container and conveying said gas into the same to accelerate the cooling of said articles after the annealing thereof.

2. The apparatus according to claim 1, wherein first sealing means are provided at the bottom of said annealing container and second sealing means at the bottom edge of said oven, said latter sealing means becoming operative for sealing said oven when said container is in hoisted position therein.-

3. The apparatus according to claim 1, wherein said cooling system includes a hood to he slipped over the annealing container in spaced relationship thereto leaving a duct for coolant to pass between said hood and said container, said hood having a plurality of air admission openings at the bottom, and an air aspirating unit placed at the top for providing air circulation through said hood.

4. The apparatus according to claim 2, wherein said cooling system includes a closed annular cooling duct 5 adjacent to the sealing means for the annealing container, and another closed annular cooling duct above said first cooling duct.

5. The apparatus according to claim 4, wherein the walls of the annealing container and the annealing oven form part of the cooling ducts.

6. The apparatus according to claim 1, wherein said cock means arranged in the lines for connecting said vacuum pump with the annealing container and annealing oven, respectively, comprises a casing and in said casing, at the side thereof facing toward the annealing container, a pressure relief valve attached to said casing.

7. The apparatus according to claim 1, including means for connecting the annealing container alternatively to said high vacuum pump and to said unit containing protective gas.

References Cited in the file of this patent UNITED STATES PATENTS 970,192 Divekey Sept. 13, 1910 1,449,472 Wesson Mar. 27, 1923 1,634,319 Callaghan July 5, 1927 1,697,144 Schonbrunn et al. Jan. 1, 1929 1,727,192 Baily Sept. 3, 1929 1,876,960 Kenworthy Sept. 13, 1932 2,450,081 Burkhardt Sept. 28, 1948 2,638,426 Brace May 12, 1953 2,810,667 Hohn et al. Oct. 22, 1957 Disclaimer 2,899,192.Kal Heinrich F m'tz, Hagen, Westphalia, Germany. APPARATUS FOR BRIGHT-ANN'EALING OF METALS. Patent dated Aug. 11, 1959. Dis claimer filed Apr. 13, 1962, by the inventor. Hereby enters this disclaimer to the entire term of said patent.

[Ofiicial Gazette M ay 29, 1.962.] 

